The present invention relates to a method and apparatus for locally smoothing the surface of bar material, such as anode bars, by clamping the bar and moving a smoothing device along its length.
Smelting electrolysis furnaces utilized in the aluminum industry employ fast-burnt block anodes consisting essentially of carbon. The block anodes are fixed at a lower end thereof by vertically arranged anode bars. The anode bars are releasably connected with a current supply. In order for good electric current transmission from the current supply to the anode bar to be achieved, at least one side of the anode bar must be a very smooth contact surface, which abuts a corresponding surface of the current supply.
During a period of operation of the furnance, it is unavoidable that the contact surface of the anode bar and the corresponding surface of the current supply will become uneven due to pits, ridges, scratches and the like resulting from current arcing and/or abrasion during installation. The result of such uneven contact surfaces is to increase electric arcs to an even greater degree, thereby impairing current transfer and furnace operation, in addition to potential safety hazards.
Surfaces of such anode bars are presently smoothed by removing the bars from the furnace and utilizing a grinding machine having a grinding belt which extends over the entire length of the bar. The grinding belt is pressed against the bar by means of a stationary guide. This method and apparatus is unsatisfactory because it not only smooths local unevenness such as pits and ridges, but also removes a significant portion of the anode bar material due to the fact that the overall length of the bar may exhibit a curvature, which is thus ground by the belt over the entire length of the bar. Such curvature in the length of the bar is not harmful to the current transfer between the current supply and the anode bar, so that the time and expense of removing such a curvature is unnecessary.
An apparatus and method for removing only local unevenness on the surface of anode bars is provided with a smoothing device which follows the general curvature of the bar as a whole. The method is practiced by an apparatus which clamps a bar to be smoothed rigidly against a frame, where a smoothing device guided by rollers abutting opposite parallel sides of the bar is attached thereto. The smoothing device is guided by the rollers along the entire length of the bar so that only local unevenness is removed, while the rollers guide the smoothing device in a path following the curvature of the overall bar length.
Accordingly, it is an object of the present invention to furnish a method and apparatus to locally remove unevenness in bar material which has a specific application to the smoothing of the surface of anode bars.
It is a further object of the present invention to minimize time and expense devoted to the smoothing of such bars by providing a roller guide for a smoothing device which allows the device to move along a surface of the bar in a path corresponding to the general curvature of the overall bar length.
The invention and its further advantages are described in greater detail in the FIGS. and following description.